Molds are generally metallic and are comprised of a body portion and a cavity portion. A key feature to increased productivity for molding operations is to dissipate the heat that is generated during the molding process. In other words, the faster one can dissipate the heat in the molding operation, the faster one can increase the cycle time for molding.
Molding is used as a technique for fabricating metallic articles such as in a shaping process. Molding is also used for the formation of thermoplastic and thermoset, as well as elastomeric materials which are generally characterized as plastic materials.
Thermal spraying is generally characterized as a group of processes in which finely divided metallic or non-metallic surfacing materials are deposited in a molten or semi-molten condition on a prepared substrate to form a spray deposit. "Thermal spraying" is a term generally applied to such other processes called arc spraying, flame spraying, and plasma spraying. The thermal spraying gun generates the necessary heat by using combustible gases or an electric arc. As the materials are heated, they change to a plastic or molten state and are accelerated by a compressed gas. The confined stream of particles are conveyed to the substrate. The particles strike the surface, flatten and form thin platelets (splats) that conform and adhere to the irregularities of the prepared surface and to each other. As the sprayed particles impinge upon the substrate, they cool and build-up, particle by particle, into a lamellar structure, thus a coating is formed. See "Thermal Spraying", Practice, Theory and Application, published by the American Welding Society, Inc. of Miami, Fla. (1995).
Plasma spraying is a thermal spraying process in which a non-transferred arc is utilized as the source of heat that ionizes a gas which melts and propels the coating material to the workpiece.
Flame spraying is a thermal spraying process in which an oxyfuel gas flame is the source of heat for melting the surfacing material. Compressed gas may or may not be used for atomizing and propelling the surfacing material to the substrate.
Arc spraying is a thermal spraying process utilizing an arc between two consumable electrodes of surfacing materials as a heat source and a compressed gas to atomize and propel the surfacing material to the substrate.
U.S. Pat. No. 3,429,962 discloses a thermal spray technique of forming a metallic oxide article. A rotatable mandrel 15 of, for example, copper or aluminum, has applied thereto a metallic oxide. The final product is obtained by chemically etching away the copper or aluminum mandrel. The end product is utilized as a fuel cell electrode. In a similar fashion, U.S. Pat. No. 5,006,321 pertains to the thermal spray method of producing glass mold plungers.
U.S. Pat. No. 4,460,529 describes the process of manufacturing a ceramic hollow body by the thermal spray technique. The ceramic bodies are comprised of aluminum and titanium carbides, borides, nitrides and mixtures thereof. The appropriate core material is selected so that it will not bind with the ceramic material. The reference indicates that the detachability of a mold core from the hollow body can be assured by the choice of a core with a higher coefficient of expansion relative to that of a ceramic or ceramic oxide layer.
U.S. Pat. No. 2,968,083 describes a hot patching of refractory structures utilizing a spraying of metal.
Other patents of interest include U.S. Pat. Nos. 5,290,373; 4,966,220; 5,000,244; 4,482,513; 4,304,747; 4,242,074; 4,547,415; 4,460,529; 3,916,418; 4,006,633; and 3,609,829.
It has been stated that spray deposits utilizing thermal spraying do not add strength to the substrate. Thermal spraying, supra at page 16. The present application, however, does utilize a body that can be cooled very quickly and the use of thermal spraying onto the body in forming the cavity of the mold allows for the design of a mold which will have extremely high strength to permit molding of plastic as well as metallic articles.
It is an object of the present invention to describe a mold or die having a body portion and a cavity portion wherein the cavity portion is formed in the body portion by means of a thermal spraying technique.
It is another object of the present invention to describe the manufacture of molds or dies having a body portion and a cavity portion wherein the cavity portion is formed by a thermal spraying technique.
It is a further object of the present invention to describe the manufacture of plastic or metallic parts by molding the desired materials in a mold that has a body portion and a cavity portion wherein the cavity portion is formed by thermal spraying metallic particles into the body portion.
It is a further object of the invention to describe a body portion of the invention which permits very high cooling rates and high flexibility in formation of a cooling means for the body.